Plasma processing apparatus and plasma processing method

ABSTRACT

A plasma processing apparatus includes: an evacuable processing chamber including a dielectric window; a substrate supporting unit, provided in the processing chamber, for mounting thereon a target substrate; a processing gas supply unit for supplying a desired processing gas to the processing chamber to perform a plasma process on the target substrate; a first RF antenna, provided on the dielectric window, for generating a plasma by an inductive coupling in the processing chamber; and a first RF power supply unit for supplying an RF power to the first RF antenna. The first RF antenna includes a primary coil provided on or above the dielectric window and electrically connected to the first RF power supply unit; 
     and a secondary coil provided such that the coils are coupled with each other by an electromagnetic induction therebetween while being arranged closer to a bottom surface of the dielectric window than the primary coil.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2009-245990 filed on Oct. 27, 2009 and U.S. Provisional Application No.61/265518 filed on Dec. 1, 2009, the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a technique for performing a plasmaprocess on a target substrate to be processed; and, more particularly,to an inductively coupled plasma processing apparatus and a plasmaprocessing method therefor.

BACKGROUND OF THE INVENTION

In the manufacturing process of a semiconductor device or a flat paneldisplay (FPD), a plasma is widely used in a process such as etching,deposit, oxidation, sputtering or the like since it has a goodreactivity with a processing gas at a relatively low temperature. Insuch plasma process, the plasma is mostly generated by a radio frequency(RF) discharge in the megahertz range. Specifically, the plasmagenerated by the RF discharge is classified into a capacitively coupledplasma and an inductively coupled plasma.

Typically, an inductively coupled plasma processing apparatus includes aprocessing chamber, at least a portion (e.g., a ceiling portion) ofwhich is formed of a dielectric window; and a coil-shaped RF antennaprovided outside the dielectric window, and an RF power is supplied tothe RF antenna. The processing chamber serves as a vacuum chambercapable of being depressurized, and a target substrate (e.g., asemiconductor wafer, a glass substrate or the like) to be processed isprovided at a central portion of the chamber. Further, a processing gasis introduced into a processing space between the dielectric window andthe substrate.

As an RF current flows though the RF antenna, an RF magnetic field isgenerated around the RF antenna, wherein the magnetic force lines of theRF magnetic field travel through the dielectric window and theprocessing space. The temporal alteration of the generated RF magneticfield causes an electric field to be induced azimuthally. Moreover,electrons azimuthally accelerated by the induced electric field collidewith molecules and/or atoms of the processing gas, to thereby ionize theprocessing gas and generate a plasma in a doughnut shape.

By increasing the size of the processing space in the chamber, theplasma is efficiently diffused in all directions (especially, in theradical direction), thereby making the density of the plasma on thesubstrate uniform. However, the uniformity of the plasma density on thesubstrate that is obtained by merely using a typical RF antenna isgenerally insufficient for the plasma process.

Accordingly, even as for the inductively coupled plasma processingapparatus, it becomes one of the most important factors to improve theuniformity of the plasma density on the substrate, since it determinesthe uniformity and the reproducibility of the plasma process itself and,furthermore, the manufacturing production yield.

Typically, in the plasma processing apparatus, the plasma density may bemade uniform in two, i.e., azimuthal and radial directions.

As for the uniformity in the azimuthal direction, since the RF antennaincludes an RF input-output terminal connected through an RF powersupply line to an RF power supply in a loop thereof, it is inevitable toemploy a nonaxisymmetric antenna configuration. This serves as a mainfactor that makes the plasma density nonuniform in the azimuthaldirection. Accordingly, the uniformity in the azimuthal direction canconventionally be improved by increasing the number of nonaxisymmetricor singularity locations of the RF antenna at a regular interval in thesame direction (see, e.g., U.S. Pat. No. 5,800,619). Alternatively, byusing two-layered series-connected coils as the RF antenna, wherein theRF power supply wire-connected locations (input-output terminals)provided in the upper coil are hidden behind the lower coil, thelocations may not be electromagnetically seen from the plasma (see,e.g., Japanese Patent Application Publication No. 2003-517197).

Moreover, as for the radial direction, the plasma density distributioncharacteristics (profile) of the plasma generated in the doughnut shapearound the dielectric window in the chamber are important and, thus, theprofile of the core plasma density distribution determines theuniformity of the plasma density distribution that can be obtained onthe substrate after the diffusion. In this regard, the conventionalmethod for dividing the RF antenna into a plurality of segments in theradial direction is mostly employed. Further, such RF antenna dividingmethod includes a first method for individually supplying RF powers tothe respective antenna segments (see, e.g., U.S. Pat. No. 5,401,350);and a second method for controlling the division ratio of the RF powerthat is divided from one RF power supply to all the antenna segments bychanging each impedance of the antenna segments in an additional circuitsuch as a capacitor or the like (see, e.g., U.S. Pat. No. 5,907,221).

However, such conventional methods for improving the uniformity of theplasma density distribution is disadvantageous in that it is difficultto manufacture any type of RF antenna for improving the uniformity inthe azimuthal or radial direction due to its complex configuration; orthe loads of the RF power supply system (RF power supply and matcher)are increased.

Especially, the conventional method for improving the uniformity in theazimuthal direction of the plasma density distribution has therestriction in the accuracy and improvement of the uniformity since anantenna portion (e.g., the lower antenna) attributable to the generationof inductive coupling plasma does not have an exactly axisymmetricshape.

SUMMARY OF THE INVENTION

In view of the above, the present invention provides an inductivelycoupled plasma processing apparatus and a plasma processing methodtherefor, capable of improving the uniformity and controllability of aplasma density distribution, with a simple configuration of its RFantenna that can easily be manufactured since loads of its RF powersupply system become small.

In accordance with an aspect of the present invention, there is provideda plasma processing apparatus. The apparatus includes: a processingchamber including a dielectric window; a substrate supporting unit,provided in the processing chamber, for mounting thereon a targetsubstrate to be processed; a processing gas supply unit for supplying adesired processing gas to the processing chamber to perform a desiredplasma process on the target substrate; a first RF antenna, provided onthe dielectric window, for generating a plasma from the processing gasby an inductive coupling in the processing chamber; and a first RF powersupply unit for supplying an RF power to the first RF antenna, the RFpower having an appropriate frequency for RF discharge of the processinggas. The first RF antenna includes a primary coil provided on or abovethe dielectric window and electrically connected to the first RF powersupply unit through an RF power supply line; and a secondary coilprovided at a portion such that the coils are coupled with each other byan electromagnetic induction therebetween, the secondary coil arrangedcloser to a bottom surface of the dielectric window than the primarycoil.

In accordance with another aspect of the present invention, there isprovided a plasma processing method. The method includes: arranging atarget substrate to be processed at a predetermined portion below adielectric window in a processing chamber including the dielectricwindow; supplying a desired processing gas to the processing chamberfrom a processing gas supply unit; maintaining a depressurized state ofthe processing chamber at a predetermined pressure level; supplying anRF power having a preset frequency from an RF power source to a primarycoil arranged on or above the dielectric window to allow an RF currentto flow through the primary coil; inducing a current through the RFcurrent by an electromagnetic induction to allow the induced current toflow through a secondary coil arranged closer to a bottom surface of thedielectric window than the primary coil; generating a plasma from theprocessing gas close to the dielectric window in the processing chamberby an induced electric field and an RF power magnetic field generated bythe induced current flowing through the secondary coil; diffusing thegenerated plasma in the processing chamber; and performing a desiredplasma process on the target substrate by using the plasma.

In the present invention, once an RF power for RF discharge is suppliedto the primary coil and, thus, the RF current flows through the primarycoil, an RF energy is transferred from the primary coil to the secondarycoil by the inductive coupling and, thus, the inductive coupling plasmais generated by the electromagnetic energy that is transferred from thesecondary coil to the processing chamber through the dielectric window.In other words, by coupling by the electromagnetic induction the primarycoil with the secondary coil and the secondary coil with the plasma inthe processing chamber, the RF power is supplied to the load, i.e., theplasma in the processing chamber through the primary coil and thesecondary coil. The secondary coil for mostly supplying theelectromagnetic energy to the processing gas in the processing chambercan be formed of one or more completely axisymmetric endless coilshaving no space-like singularity (power-supply point).

Accordingly, it is possible to make the plasma density of the plasmagenerated in the doughnut shape in the processing space of theprocessing chamber uniform in the azimuthal direction and, furthermore,the density distribution of the plasma around the substrate supportingunit (i.e., on the semiconductor wafer W) uniform in the azimuthaldirection.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention will become apparentfrom the following description of embodiments, given in conjunction withthe accompanying drawings, in which:

FIG. 1 is a longitudinal cross sectional view showing a configuration ofan inductively coupled plasma etching apparatus in accordance with anembodiment of the present invention;

FIG. 2 is a perspective view showing main elements of a plasmageneration unit in the inductively coupled plasma etching apparatusshown in FIG. 1;

FIG. 3A is a perspective view showing a concentric coil;

FIG. 3B is a perspective view showing a spiral coil;

FIG. 4A is a schematic cross sectional view showing a first modificationof the layout configuration of an RF antenna in accordance with thepresent embodiment;

FIG. 4B is a schematic cross sectional view showing a secondmodification of the layout configuration of the RF antenna in accordancewith the present embodiment;

FIG. 4C is a schematic cross sectional view showing a third modificationof the layout configuration of the RF antenna in accordance with thepresent embodiment;

FIG. 4D is a schematic cross sectional view showing a fourthmodification of the layout configuration of the RF antenna in accordancewith the present embodiment;

FIG. 4E is a schematic cross sectional view showing a fifth modificationof the layout configuration of the RF antenna in accordance with thepresent embodiment;

FIG. 5 shows a modification of an RF power supply layout of the RFantenna in accordance with the present embodiment;

FIG. 6 shows another modification of the RF power supply layout of theRF antenna in accordance with the present embodiment;

FIG. 7A a perspective view schematically showing an example of anantenna layout configuration in the case of including a plurality of RFantennas;

FIG. 7B is a schematic cross sectional view showing the antenna layoutconfiguration;

FIG. 8A is a perspective view showing how capacitors are respectivelyprovided in loops of the RF antennas in accordance with the presentembodiment;

FIG. 8B is a top view showing how the capacitors are respectivelyprovided in the loops of the RF antennas in accordance with the presentembodiment;

FIG. 9A is a contour plot diagram showing a distribution of an inducedcurrent that is excited in a plasma in a test example and a comparisonexample;

FIG. 9B is a circling plot diagram showing the distribution of theinduced current that is excited in the plasma in the test example andthe comparison example;

FIG. 10 is a bar graph showing a ratio of an induced (secondary) currentflowing through an endless coil provided at each radial position of asecondary coil to an RF (primary) current flowing through a primary coilin the test example;

FIG. 11 is a graph showing a radial distribution of the density of acurrent that is excited in the plasma when an RF current of 1 A issupplied to the primary coil in the test example and the comparisonexample;

FIG. 12A is a bar graph showing a ratio of an induced (secondary)current flowing through an endless coil provided at each radial positionof the secondary coil to an RF (primary) current flowing through theprimary coil in a first capacitance adjusting example of the testexample;

FIG. 12B is a graph showing a radial distribution of the density of acurrent that is excited in the plasma when an RF current of 1 A issupplied to the primary coil in the first capacitance adjusting exampleof the test example;

FIG. 13A is a bar graph showing a ratio of an induced (secondary)current flowing through an endless coil provided at each radial positionof the secondary coil to an RF (primary) current flowing through theprimary coil in a second capacitance adjusting example of the testexample;

FIG. 13B is a graph showing a radial distribution of the density of acurrent that is excited in the plasma when an RF current of 1 A issupplied to the primary coil in the second capacitance adjusting exampleof the test example;

FIG. 14A is a bar graph showing a ratio of an induced (secondary)current flowing through an endless coil provided at each radial positionof the secondary coil to an RF (primary) current flowing through theprimary coil in a third capacitance adjusting example of the testexample;

FIG. 14B is a graph showing a radial distribution of the density of acurrent that is excited in the plasma when an RF current of 1 A issupplied to the primary coil in the third capacitance adjusting exampleof the test example;

FIG. 15A is a bar graph showing a ratio of an induced (secondary)current flowing through an endless coil provided at each radial positionof the secondary coil to an RF (primary) current flowing through aprimary coil in a fourth capacitance adjusting example of the testexample;

FIG. 15B is a graph showing a radial distribution of the density of acurrent that is excited in the plasma when an RF current of 1 A issupplied to the primary coil in the fourth capacitance adjusting exampleof the test example;

FIG. 16A is a bar graph showing a ratio of an induced (secondary)current flowing through an endless coil provided at each radial positionof the secondary coil to an RF (primary) current flowing through theprimary coil in a fifth capacitance adjusting example of the testexample;

FIG. 16B is a graph showing a radial distribution of the density of acurrent that is excited in the plasma when an RF current of 1 A issupplied to the primary coil in the fifth capacitance adjusting exampleof the test example;

FIGS. 17A to 17D stepwisely show a process of a multilayer resistmethod;

FIG. 18 is a perspective view showing a test example where the secondarycoil is rotated in the inductively coupled plasma etching apparatus inaccordance with the present embodiment; and

FIG. 19 is a top view showing a modification of a coil configuration ofthe secondary coil in accordance with the present embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will now be described withreference to the accompanying drawings which form a part hereof.

FIG. 1 shows a configuration of an inductively coupled plasma etchingapparatus in accordance with an embodiment of the present invention. Theinductively coupled plasma etching apparatus is of a type using a planarcoil type RF antenna, and includes a cylindrical vacuum chamber(processing chamber) 10 made of a metal, e.g., aluminum, stainless steelor the like. The chamber 10 is frame-grounded.

In the inductively coupled plasma etching apparatus, various unitshaving no involvement in plasma generation will be described first. At alower central portion of the chamber 10, a circular plate-shapedsusceptor 12 for mounting thereon a target substrate, e.g., asemiconductor wafer W as a substrate supporting table is horizontallyarranged. The susceptor 12 also serves as an RF electrode. The susceptor12, which is made of, e.g., aluminum, is supported by an insulatingtubular support 14 uprightly extending from a bottom portion of thechamber 10.

A conductive tubular support part 16 is provided uprightly extendingfrom the bottom portion of the chamber 10 along the periphery of theinsulating tubular support 14, and an annular exhaust path 18 is definedbetween the support part 16 and an inner wall of the chamber 10.Moreover, an annular baffle plate 20 is attached to an entrance or a topportion of the exhaust path 18, and an exhaust port 22 is provided at abottom portion thereof.

To allow a gas to uniformly flow in the chamber 10 axisymmetrically withregard to the semiconductor wafer W on the susceptor 12, it ispreferable to provide a plural number of exhaust ports 22 at a regularinterval circumferentially. The exhaust ports 22 are connected to anexhaust device 26 via respective exhaust pipes 24. The exhaust device 26includes a vacuum pump such as a turbo molecular pump to evacuate aplasma-processing space in the chamber 10 to a predetermined vacuumlevel. Attached to the sidewall of the chamber 10 is a gate valve 28 foropening and closing a loading/unloading port 27.

An RF power supply 30 for an RF bias is electrically connected to thesusceptor 12 via a matcher 32 and a power supply rod 34. The RF powersupply 30 outputs a variable RF power RF_(L) of an appropriate frequency(e.g., 13.56 MHz or less) to control the energy for attracting ionstoward the semiconductor wafer W. The matcher 32 includes avariable-reactance matching circuit for performing the matching betweenthe impedances of the RF power supply 30 and the load (mainly,susceptor, plasma and chamber), and the matching circuit includes ablocking capacitor for generating a self-bias.

An electrostatic chuck 36 is provided on an upper surface of thesusceptor 12 to hold the semiconductor wafer W by an electrostaticattraction force, and a focus ring 38 is provided around theelectrostatic chuck 36 to annularly surround the periphery of thesemiconductor wafer W. The electrostatic chuck 36 includes an electrode36 a made of a conductive film and a pair of dielectric films 36 b and36 c. A high voltage DC power supply 40 is electrically connected to theelectrode 36 a via a switch 42 by using a coated line 43. By applying ahigh DC voltage from the DC power supply 40 to the electrode 36 a, thesemiconductor wafer W can be attracted to and held on the electrostaticchuck 36 by the electrostatic force.

A coolant path 44, which extends in, e.g., a circumferential direction,is provided inside the susceptor 12. A coolant, e.g., a cooling water,of a predetermined temperature is supplied from a chiller unit (notshown) to the coolant path 44 to be circulated through pipelines 46 and48. By adjusting the temperature of the coolant, it is possible tocontrol a process temperature of the semiconductor wafer W held on theelectrostatic chuck 36.

Moreover, a heat transfer gas, e.g., He gas, is supplied from a heattransfer gas supply unit (not shown) to a space between a top surface ofthe electrostatic chuck 36 and a bottom surface of the semiconductorwafer W through a gas supply line 50. Further, an elevating mechanism(not shown) including lift pins capable of being moved up and down whilevertically extending through the susceptor 12 and the like is providedto load and unload the semiconductor wafer W.

Next, various units having involvement in the plasma generation in theinductively coupled plasma etching apparatus will be described. FIG. 2shows main elements of a plasma generation unit in the inductivelycoupled plasma etching apparatus.

A ceiling of the chamber 10 is separated from the susceptor 12 at arelatively large distance, and a circular dielectric window 52 formedof, e.g., a quartz plate is airtightly provided in the ceiling. As asingle unit with the chamber 10, an antenna chamber 56 for accommodatingan RF antenna 54 while electronically shielding it from the outside isprovided on the dielectric window 52. The RF antenna 54 is used togenerate an inductively coupled plasma in the chamber 10.

In the present embodiment, the RF antenna 54 includes a primary coil 62arranged above and separated from the dielectric window 52 and connectedto an RF power supply line 60 of an RF power supply unit 58; and asecondary coil 64 arranged at a portion such that the coils 62 and 64can be coupled with each other by the electromagnetic inductiontherebetween while being electrically floated from the primary coil 62closer to a bottom surface (i.e., a surface facing the processing space)of the dielectric window 52 than the primary coil 62.

In FIG. 2, the secondary coil 64 is horizontally mounted on the topsurface of dielectric window 52, and the primary coil 62 is horizontallymounted on a support plate 66 formed of an insulator, provided above andseparated from the secondary coil 64 at an appropriate distance.Typically, the coils 62 and 64 are arranged to be concentric with eachother horizontally and, furthermore, with the chamber 10 and thesusceptor 12 horizontally.

Preferably, the primary coil 62 formed of, e.g., a multi-wound coil hasa concentric shape with regular radiuses as shown in FIGS. 2 and 3A.Alternatively, the primary coil 62 may have another shape, e.g., aspiral shape shown in FIG. 3E. Typically, a central end portion of theprimary coil 62 is connected to the RF power supply line of the RF powersupply unit 58, and a peripheral end portion is electrically connectedto a ground potential through a ground line 68. The primary coil 62 ispreferably made of, e.g., a copper-based metal having a highconductivity.

Preferably, as shown in FIG. 2A, the secondary coil 64 is, e.g., acombination coil including a plurality of, e.g., three, endless coils64(1) to 64(3) having different diameters that are concentricallyarranged. Each of the endless coils 64(1) to 64(3) is preferably madeof, e.g., a copper-based metal having a high conductivity.Alternatively, the endless coils 64(1) to 64(3) may be made of, e.g., asemiconductor such as Si or SiC.

In FIG. 2, the primary coil is formed of the concentric coil that iswound three times. An inner wound portion 62(1), an intermediate woundportion 62(2) and an outer wound portion 62(3) of the primary coil 62are respectively arranged to vertically opposite to the inner endlesscoil 64(1), the intermediate endless coil 64(2) and the outer endlesscoil 64(3) of the secondary coil 64.

The RF power supply unit 58 includes an RF power supply 70 and a matcher72 and outputs a variable RF power RF_(H) of an appropriate frequency(e.g., 13.56 MHz or more) for plasma generation by RF discharge. Thematcher 72 includes a variable-reactance matching circuit for performingthe matching between the impedances of the RF power supply 70 and theload (mainly, RF antenna, plasma and correction coil).

A processing gas supply unit for supplying a processing gas to thechamber 10 includes an annular manifold or buffer unit 74 providedinside (or outside) the sidewall of the chamber 10 to be located at aplace slightly lower than the dielectric window 52; a plurality ofsidewall gas injection holes 76 circumferentially formed on the sidewallat a regular interval and opened to the plasma-generation space from thebuffer unit 74; and a gas supply line 80 extended from a processing gassupply source 78 to the buffer unit 74. The processing gas supply source78 includes a mass flow controller and an on-off valve, which are notshown.

A main control unit 82 includes, e.g., a microcomputer and controls theoverall operation (sequence) of the plasma etching apparatus andindividual operations of various units, e.g., the exhaust device 26, theRF power supplies 30 and 70, the matchers 32 and 72, the switch 42 ofthe electrostatic chuck, the processing gas supply source 78, thechiller unit (not shown), the heat-transfer gas supply unit (not shown)and the like.

When the inductively coupled plasma etching apparatus performs anetching process, the gate valve 28 is first opened to load a targetsubstrate, i.e., a semiconductor wafer W, into the chamber 10 and mountit onto the electrostatic chuck 36. Then, the gate valve 28 is closed,and an etching gas (typically, a gaseous mixture) is introduced from theprocessing gas supply source 78, via the buffer unit 74, into thechamber 10 at a preset flow rate and flow rate ratio through thesidewall gas injection holes 76 by using the gas supply line 80.Thereafter, the RF power supply 70 of the RF power supply unit 58 isturned on to output a plasma-generating RF power RF_(H) at apredetermined RF level, so that a current of the RF power RF_(H) issupplied to the primary coil 62 of the RF antenna 54 through the RFpower supply line 60 via the matcher 72. In addition, the RF powersupply 30 is turned on to output an ion-attracting control RF powerRF_(L) at a predetermined RF level, so that the RF power RF_(L) issupplied to the susceptor 12 through the power supply rod 34 via thematcher 32.

Further, a heat-transfer gas (i.e., He gas) is supplied from theheat-transfer gas supply unit to a contact interface between theelectrostatic chuck 36 and the semiconductor wafer W, and the switch isturned on, so that the heat-transfer gas is confined in the contactinterface by the electrostatic attraction force of the electrostaticchuck 36.

The etching gas injected through the sidewall gas injection holes 76 isuniformly diffused in the processing space below the dielectric window52. At this time, magnetic force lines (magnetic flux) generated aroundthe primary coil 62 by the current of the RF power RF_(H) flowingthrough the primary coil 62 of the RF antenna 54 are interlinked withthe secondary coil 64, so that an electromotive force is induced in thesecondary coil by the temporal alteration of the generated magneticflux, thereby allowing a current (i.e., an induced current) to flow inthe loop.

Magnetic force lines are generated by the induced current flowingthrough the secondary coil 64, and the generated magnetic force linestravel through dielectric window 52 and across the processing space(plasma generation space) of the chamber 10, to thereby induce anelectric field azimuthally in the processing space. Electronsazimuthally accelerated by the induced electric field collide withmolecules and/or atoms in the etching gas, to thereby ionize the etchinggas and generate a plasma in a doughnut shape. As such, the plasma isdominantly generated by the electric field caused by the secondary coil64, while it is hardly affected by the primary coil 62.

Here, the expression “plasma in a doughnut shape” indicates not only astate where the plasma is generated only at the radially outer portionin the chamber 10 without being generated at the radially inner portion(at the central portion) therein but also a state where the volume ordensity of the plasma generated at the radially outer portion becomeslarger than that at the radially inner portion. Moreover, if the kind ofthe processing gas, the pressure inside the chamber 10 and/or the likeare changed, the plasma may be generated in another shape instead of thedoughnut shape.

In the wide processing space, radicals and ions of the plasma generatedin the doughnut shape are diffused in all directions, so that theradicals isotropically pour down and the ions are attracted by the DCbias onto a top surface (target surface) of the semiconductor wafer W.Accordingly, plasma active species cause chemical and physical reactionson the target surface of the semiconductor wafer W, thereby etching atarget film into a predetermined pattern. In the present embodiment, aswill be described later, it is possible to significantly improve theradial uniformities in the plasma process properties in the azimuthaldirection as well as in the radial direction, i.e., etching properties(etching rate, selectivity, etching shape and the like), of thesemiconductor wafer W.

As such, in the inductively coupled plasma etching apparatus of thepresent embodiment, the RF antenna 54 provided above a ceiling window(in the antenna chamber 56) of the chamber 10 includes the primary coil62 and the secondary coil 64 arranged one above the other and completelyseparated from each other. Accordingly, once an RF power RF_(H) for theRF discharge is supplied from the RF power supply unit 58 to the primarycoil 62, the energy is transferred by the inductive coupling between thecoils 62 and 64 and, thus, an inductively coupled plasma is generated bythe electromagnetic energy that is discharged from the secondary coil 64into the processing gas in the chamber 10 by traveling throughdielectric window 52.

In other words, by coupling by the electromagnetic induction the coils62 and 64 with each other and the secondary coil 64 with the plasma inthe chamber 10, the RF power RF_(H) is supplied to the load, i.e., theplasma in the chamber 10 through the coils 62 and 64.

With such method for supplying an RF power to a plasma through theinductive coupling between a plurality of coils, it is possible toprovide the final stage coil, i.e., the secondary coil 64 for supplyingthe electromagnetic energy to the processing gas in the chamber 10through the dielectric window 52, serving as a completely axisymmetricendless coil having no space-like singularity (power-supply point).Accordingly, it is possible to make the plasma density of the plasmagenerated in the doughnut shape in the processing space of the chamber10 uniform in the azimuthal direction and, furthermore, the densitydistribution of the plasma around the susceptor 12 (i.e., on thesemiconductor wafer W) uniform in the azimuthal direction.

Further, since each of the coils 62 and 64 has a simple configuration,it is possible to easily manufacture the coils 62 and 64. No significantload is applied to the RF power supply unit 58.

Besides, since the primary coil 62 includes an input-output terminal forRF power supply and is not an axisymmetric coil, the magnetic fluxinterlinked with the secondary coil 64, i.e., a magnetic field generatedaround the primary coil 62 by the RF power RF_(H) flowing through theprimary coil 62, is not uniform in the azimuthal direction. However, theinduced current flowing through the secondary coil 64 is the same at anyportion of the loop, and the secondary coil 64 is an axisymmetriccircular endless coil. Accordingly, a magnetic field generated aroundthe secondary coil 64 (specifically, in the chamber 10) by the inducedcurrent flowing therethrough becomes uniform over one period in theazimuthal direction.

In the RF antenna 54 of the present embodiment, the planar primary coil62 is horizontally arranged above the dielectric window 52, and theplanar secondary coil 64 is horizontally mounted on the top surface ofthe dielectric window 52. However, in the present invention, such layoutconfiguration of the RF antenna 54 is merely an example, and variousmodifications may be made instead.

As described above, the secondary coil 64 is formed of one or moreendless coils 64(1) to 64(3), and the line connection to the outside isunnecessary. Accordingly, as shown in FIG. 4A, the secondary coil 64(endless coils 64(1) to 64(3)) may be buried in the dielectric window52. In this case, as the layout configuration shown in FIG. 4B, it ispreferable to provide each of the endless coils 64(1) to 64(3) atindependent height positions. Alternatively, one part of the secondarycoil 64 (endless coils 64(1) to 64(3)) may be provided in the dielectricwindow 52, and the other part thereof may be provided on the dielectricwindow 52.

Similarly, the primary coil 62 is not limited to the planar type. Forexample, as shown in FIG. 4B, the height positions of the wound portions62(1) to 62(3) may preferably be changed depending on those of thecorresponding endless coils 64(1) to 64(3) in such a way that theoverall valance and the efficiency of the inductive coupling between thewound portions 62(1) to 62(3) and the corresponding endless coils 64(1)to 64(3) can be optimized.

Further alternatively, as shown in FIG. 4C, one part, e.g., the outerendless coil 64(3) of the endless coils 64(1) to 64(3) of the secondarycoil 64 may be arranged immediately below the dielectric window 52,i.e., a plasma-generation area in the chamber 10. However, in case thatthe endless coil 64(3) is made of, e.g., a metal such as copper, it ispreferable to cover the endless coil 64(3) with an anti-contaminationhollow ring cover 84 made of, e.g., quartz.

Further, in case that the secondary coil 64 is provided in thedielectric window 52 or the chamber 10, the primary coil 62 may bearranged closest to the dielectric window 52. For example, as shown inFIG. 4C, the primary coil 62 may be arranged on the top surface of thedielectric window 52.

As another layout configuration shown in FIGS. 4D and 4E, in case thateach of the endless coils 64(1) to 64(3) of the secondary coil 64 ismade of, e.g., Si or SiC, the endless coils 64(1) to 64(3) may beexposed without being covered with in the hollow ring cover and arrangedon the bottom surface of the dielectric window 52 or in theplasma-generation area.

In the present embodiment, there may be various modifications of thesupplying method for supplying the RF power RF_(H) to the primary coil62 of the RF antenna 54.

In the RF antenna 54 shown in FIG. 2, the wound portions 62(1) to 62(3)of the primary coil 62 are connected in series to the single RF powersupply unit 58.

However, as shown in FIG. 5, the wound portions 62(1) to 62(3) may beconnected in parallel to the single RF power supply unit 58. In thiscase, the current of the RF power RF_(H) supplied from the RF powersupply unit 58 is branched into the wound portions 62(1) to 62(3).Relatively large current is supplied to the wound portion having arelatively low impedance (typically, the internal wound portion 62(1)),and relatively small current is supplied to the wound portion having arelatively high impedance (typically, the outer wound portion 62(3)).

Alternatively, as shown in FIG. 6, the wound portions 62(1) to 62(3) mayrespectively be connected to a plurality of the RF power supply units58(1) to 58(3). In this case, RF currents or RF current powers mayrespectively be supplied from the RF power supply units 58(1) to 58(3)to the wound portions 62(1) to 62(3) regardless of their relativeimpedances.

Further alternatively, as shown in FIGS. 7A and 7B, an additional RFantenna 86 that is independent of the RF antenna 54 may be arrangedaround the dielectric window 52. In FIGS. 7A and 7B, the RF antennas 54and 86 are respectively arranged at the radially inner portion (centralportion) and the radially outer portion (peripheral portion) of thedielectric window 52. The RF antenna 86 may be a single-wound (ormulti-wound) concentric coil as shown above or a spiral coil.Preferably, dedicated RF power supply units 58(1) and 58(2) arerespectively provided to supply RF currents of different levels to bothof the RF antennas 54 and 86. However, the RF current supplied from thesingle RF power supply unit 58 may be divided into two RF currents to besupplied to the RF antennas 54 and 86.

Meanwhile, a capacitor may preferably be provided in the loop of thesecondary coil 64 of the RF antenna 54. In case that the secondary coil64 is formed of the endless coils 64(1) to 64(3), the capacitor may beprovided in the loop of one (e.g., the endless coil 64(3)) or the loopsof all the endless coils 64(1) to 64(3). Specifically, a cutout having agap width of, e.g., 5 mm may be formed at a circumferential location ofeach coil conductor of the endless coil 64(1) to 64(3), and a capacitormay be provided at each of the cutouts. FIGS. 8A and 8B show an examplewhere capacitors 90(1) to 90(3) are respectively provided in the loopsof the endless coils 64(1) to 64(3).

Following electromagnetic field simulations were performed by thepresent inventors for the inductively coupled plasma etching apparatusof the present embodiment.

In other words, as a result of obtaining the distribution of an inducedcurrent that was excited in a plasma in the inductively coupled plasmaetching apparatus shown in FIG. 1 where capacitors were inserted intothe secondary coil 64, the characteristics shown in FIG. 9A (contourplot diagram) and FIG. 9B (circling plot diagram) were obtained. InFIGS. 9A and 9B, the distributions of the induced currents excited inthe plasma were shown in the cases that no secondary coil 64 wasprovided and the primary coil 62 was provided on the top surface of thedielectric window 52 as a comparison example; and the coils 62 and 64and the capacitors 90(1) to 90(4) were provided as a test example, inthe inductively coupled plasma etching apparatus shown in FIG. 1.

In the electromagnetic field simulations, the primary coil 62 was formedof a concentric coil that was wound four times, where a first, a second,a third and a fourth wound portion had radials of about 70, 120, 170 and220 mm, respectively. Conforming to the coil configuration of theprimary coil 62, the secondary coil 64 included four concentricallyarranged endless coils 64(1) to 64(4) having radials of about 70, 120,170 and 220 mm, respectively.

In addition, in the electromagnetic field simulations, the secondarycoil 64 was arranged on the top surface of the dielectric window 52, andthe primary coil 62 was arranged above and at a distance of about 5 mmfrom the secondary coil 64. The capacitors 90(1) to 90(4) respectivelyhad the capacitances of about 1547, 650, 400 and 250 pF. As the plasmagenerated in the doughnut by the inductive coupling in the processingspace, a disk-shaped resistance was simulated, where its radius,resistivity and skin thickness were set to be about 250 mm, 100 Ωcm and10 mm, respectively. The plasma-generating RF power RF_(H) had afrequency of about 13.56 MHz.

As shown in FIGS. 9A and 9B, in the comparison example, it was seen thatthere was a bias in the induced current in the plasma approximately inthe 9 o'clock direction (the 180° direction based on the forwarddirection of the X-axis in the circling direction) corresponding to aportion of an RF power supply input/output terminal of the primary coil62. On the other hand, in the test example, it was seen that there wasno bias in the circling direction. Further, it has been known that theinduced current in the plasma which is nonuniform in the radialdirection results in a uniform plasma density in the diametricaldirection after the diffusion.

Additionally, in the test example of the electromagnetic fieldsimulations, as the result of obtaining the induced (secondary) currentflowing through each of the endless coils 64(1) to 64(4) of thesecondary coil 64 when an RF (primary) current of 1 A was supplied tothe primary coil 62 in the RF antenna 54, the graph shown in FIG. 10showing the ratio of the induced (secondary) current of each radialposition to the RF (primary) current was obtained. FIG. 10 indicatesthat the induced (secondary) current increased about one to five timesas much as the RF (primary) current flowed at each radial position.

Moreover, in the test example and the comparison example, thecharacteristics shown in FIG. 11 were obtained as the result of analysison a radial distribution of the density (corresponding to the plasmadensity) of a current excited in the plasma. FIG. 11 indicates thatthere was the difference by about five times at the maximum in thecurrent density in the plasma depending on whether or not the secondarycoil 64 existed and, resultantly, a large current could be generated inthe plasma by the current multiplication effect.

Typically, in the inductive coupling method, it is required to increasethe winding density of an antenna or a coil in order to increase acurrent excited in the plasma. This, however, inevitably extends thelength of the coil, causing the wavelength effect. On the other hand, inthe present embodiment, it is possible to increase the current excitedin the plasma without increasing the winding density. Further, since itis sufficient to supply a small current from the matcher 72 of the RFpower supply unit 58 to the primary coil 62, it is possible to easilyperform the matching while preventing a power loss in the matcher 72.

In the present embodiment, it is preferable to employ variablecapacitors as the capacitors provided in the loop of the secondary coil64. In the electromagnetic field simulations, variable capacitors wereemployed for the capacitors 90(1) to 90(4) respectively provided in theloops of the endless coils 64(1) to 64(4), and the induced (secondary)current flowing through each radial position of the endless coils 64(1)to 64(4) was obtained by variously changing the each capacitance of thecapacitors 90(1) to 90(4) with a plurality of combinations. Resultantly,the characteristics shown in FIGS. 12A to 16B were obtained as theradial distribution of the densities of currents generated in the plasmaand the ratios of the induced (secondary) currents of respective radialpositions to the RF (primary) currents of the primary coil 62.

(First Capacitance Adjusting Example)

In case that the capacitances of the capacitors 90(1) to 90(4) wererespectively set to be 1547, 650, 400 and 250 pF, the results shown inFIGS. 12A and 12B were respectively obtained as the ratios of theinduced (secondary) currents to the RF (primary) currents and the radialdistribution of the density of currents generated in the plasma.

Specifically, as shown in FIG. 12A, the largest current flowed throughthe endless coil 64(3) (r=170 mm), and the smallest current flowedthrough the endless coil 64(1) (r=70 mm). Intermediate currentsrespectively flowed through the endless coils 64(2) (r=120) and 64(3)(r=220). Moreover, as shown in FIG. 12B, the radial distribution of thedensity of currents generated in the plasma showed a profile of therelative magnitude relationship of the induced currents of the fourrespective radial positions. That is, the density of currents generatedin the plasma showed a mountain-shaped profile in which it had asignificantly great value around a portion r=170 mm.

(Second Capacitance Adjusting Example)

In case that the capacitances of the capacitors 90(1) to 90(4) wererespectively set to be 3000, 300, 300 and 380 pF, the results shown inFIGS. 13A and 13B were respectively obtained as the ratios of theinduced (secondary) currents to the RF (primary) currents and the radialdistribution of the density of currents generated in the plasma.

Specifically, as shown in FIG. 13A, the largest current flowed throughthe endless coil 64(4) (r=220 mm), and currents of magnitudes of about ⅓of that of the largest current respectively flowed through the otherendless coils 64(1) to 64(3) (r=70, 120 and 170). Moreover, as shown inFIG. 13B, the radial distribution of the density of currents generatedin the plasma showed a profile of the relative magnitude relationship ofthe induced currents of the four respective radial positions. That is,the density of currents generated in the plasma showed a profile inwhich the current density of a portion (r=70 mm) closer to the center inthe radial direction tended to become lower than that of an intermediateportion (r=120 to 170) in the radial direction.

(Third Capacitance Adjusting Example)

In case that the capacitances of the capacitors 90(1) to 90(4) wererespectively set to be 1547, 650, 300 and 380 pF, the results shown inFIGS. 14A and 14B were respectively obtained as the ratios of theinduced (secondary) currents to the RF (primary) currents and the radialdistribution of the density of currents generated in the plasma.

Specifically, as shown in FIG. 14A, the induced currents were dividedinto two groups. That is, larger currents flowed respectively throughthe endless coils 64(2) and 64(4) (r=120 and 220 mm), and smallercurrents respectively flowed through the endless coils 64(1) to 64(3)(r=70 and 170). Moreover, as shown in FIG. 14B, the radial distributionof the density of currents generated in the plasma showed a profile ofthe relative magnitude relationship of the induced currents of the fourrespective radial positions. That is, the density of currents generatedin the plasma showed a profile in which it had local maximum valuesaround two intermediate portions (r=120 and 170 mm, respectively) in theradial direction.

(Fourth Capacitance Adjusting Example)

In case that the capacitances of the capacitors 90(1) to 90(4) wererespectively set to be 1400, 500, 586 and 380 pF, the results shown inFIGS. 15A and 15B were respectively obtained as the ratios of theinduced (secondary) currents to the RF (primary) currents and the radialdistribution of the density of currents generated in the plasma.

Specifically, as shown in FIG. 15A, the largest current flowed throughthe endless coil 64(1) (r=70 mm), and currents of magnitudes of about ⅗of that of the largest current respectively flowed through the otherendless coils 64(2) to 64(4) (r=120, 170 and 220). Moreover, as shown inFIG. 15B, the radial distribution of the density of currents generatedin the plasma showed a profile of the relative magnitude relationship ofthe induced currents of the four respective radial positions. Thedensity of currents generated in the plasma was significantly decreasedaround an intermediate portion (r=120 to 170 mm) in the radialdirection.

(Fifth Capacitance Adjusting Example)

In case that the capacitances of the capacitors 90(1) to 90(4) wererespectively set to be 1547, 300, 300 and 380 pF, the results shown inFIGS. 16A and 16B were respectively obtained as the ratios of theinduced (secondary) currents to the RF (primary) currents and the radialdistribution of the density of currents generated in the plasma.

Specifically, as shown in FIG. 16A, the largest current flowed throughthe endless coil 64(4) (r=220 mm), and a current of magnitude of about ⅔of that of the largest current flowed through the endless coil 64(1)(r=70 mm). Currents of magnitudes of about ⅓ of that of the largestcurrent respectively flowed through the endless coils 64(2) and 64(3)(r=120 and 170). Moreover, as shown in FIG. 16B, the radial distributionof the density of currents generated in the plasma showed a profile ofthe relative magnitude relationship of the induced currents of the fourrespective radial positions.

As described above, in the inductively coupled plasma etching apparatusof the present embodiment, by providing variable capacitors in the loopsof the secondary coil 64 in the RF antenna 54 and changing thecapacitances of the variable capacitors, it is possible to control theradial distribution of the density of the current excited in the plasma(i.e., the plasma density in the plasma generated in the doughnut shape)and, furthermore, to arbitrarily or multifariously control the radialdistribution of the plasma density at a portion close to the susceptor12 (on the semiconductor wafer W). Accordingly, it is possible toimprove the uniformity of the plasma density and, furthermore, theuniformity of the plasma process even in the radial direction.

The inductively coupled plasma etching apparatus of the presentembodiment may be appropriately applied to the application in which amultilayered film on the surface of a target substrate is continuouslyetched at a plurality of steps.

Hereinafter, a multilayer resist method shown in FIGS. 17A to 17D inaccordance with another embodiment of the present invention will bedescribed.

As shown in FIGS. 17A to 17D, in a main surface of the semiconductorwafer W serving as a target substrate to be processed, an SiN layer 102serving as a lowermost layer (final mask) is formed on an originaltarget film (e.g., a gate Si film) to be processed. An organic film(e.g., carbon film) 104 serving as an intermediate layer is formed onthe SiN layer 102. A photoresist 108 serving as an uppermost layer isformed on the organic film 104 via a Si-containing bottomanti-reflective coating (BARC) film 106. The SiN layer 102, the organicfilm 104 and the BARC film 106 are formed by using the chemical vapordeposition (CVD) or the spin-on coating method. The photoresist 108 ispatterned by the photolithography.

First, in a first etching process step, as shown in FIG. 17A, theSi-containing BARC film 106 is etched by using the patterned photoresist108 as a mask. In this case, a gaseous mixture of CF₄ and O₂ is employedas an etching gas, and the pressure inside the chamber 10 is set to berelatively low, e.g., 10 mTorr.

Next, in a second etching process step, as shown in FIG. 17B, theorganic film 104 is etched by using as a mask the photoresist 108 andthe BARC film. In this case, a single O₂ gas is employed as an etchinggas, and the pressure inside the chamber 10 is set to be relativelylower, e.g., 5 mTorr.

Finally, in a third etching process step, as shown in FIGS. 17C and 17D,the SiN 102 is etched by using as a mask the patterned BARC 106 and theorganic film 104. In this case, a gaseous mixture of CHF₃, CF₄, Ar andO₂ is employed as an etching gas, and the pressure inside the chamber 10is set to be relatively high, e.g., 50 mTorr.

In such multiple etching process steps, the process conditions areentirely or partially (especially, the pressure in the chamber 10)changed and, thus, the plasma generated in the doughnut shape isdiffused in another form in the processing space. Here, in case that nosecondary coil 64 is provided, the electron density (plasma density)around the susceptor 12 in the first and the second step (pressure of 10mTorr or less) show a precipitous mountain-shaped profile in which ithas a relatively significantly high value at the central portion. Theelectron density in the third step (pressure of 50 mTorr) has a gentlemountain-shaped profile in which it has a slightly high value at thecentral portion.

In accordance with the present embodiment, in, e.g., a process recipe,the capacitances of the capacitors 90(1) to 90(n) (e.g., n=4) are set asone of the process parameters or recipe information in order to add thecapacitances into the typical process conditions (the magnitude of theRF power, pressure, gas type, gas flow rate and the like). Then, whenthe multiple etching process steps are performed, the main control unit74 reads out data corresponding to the capacitances of the capacitors90(1) to 90(n) from a memory and, at each step, sets the capacitances ofthe capacitors 90(1) to 90(n) to preset (target) values.

Accordingly, in the etching process steps of the multilayer resistmethod, the first step (10 mTorr), the second step (5 mTorr) and thethird step (50 mTorr) are respectively converted into the first, thesecond and the third capacitance adjusting example.

As such, it is possible to variously control the capacitances of thecapacitors 90(1) to 90(n) depending on the adjustment, the conversionand the change of the process conditions during the single plasmaprocess or the multiple plasma processes of one semiconductor wafer W.Accordingly, it is possible to improve the uniformity of the plasmaprocess by multifariously or optimally the radial distribution of aplasma density around the susceptor 12 (on the semiconductor wafer W)through the entire processing time or the entire steps of thesingle-wafer plasma process.

FIG. 18 schematically shows a test example where the secondary coil 64of the RF antenna 54 is rotated in the inductively coupled plasmaetching apparatus of the present embodiment. As described above, in casethat the capacitors are provided in the loops of the secondary coil 64,the asymmetric property of the secondary coil 64 may become lost at theportions where the capacitors are provided, and a bias may be generatedin the plasma density distribution in the circling direction.

In this case, by rotating the secondary coil 64 about its central axis,it is possible to temporally make uniform the electric variationsgenerated in the loops of the secondary coil 64, to thereby improve theuniformity of the plasma density distribution in the circling(azimuthal) direction. As described above, since the secondary coil isformed of completely closed loops without requiring the line connectionto the outside, it is possible to rotate the secondary coil 64 only orthe secondary coil 64 and a supporting unit 110 only.

In FIG. 18, a rotating mechanism includes the supporting unit 110 formedof a dielectric circular plate body; a rotation ring 114 coupled to thesupporting unit 110; a pulley or pinion 116; and a rotational drivingunit 118 having a motor for rotating the rotation ring 114 via thepinion 116.

The layout configuration of the secondary coil 64 is not limited to theabove-mentioned case where one or more endless coils 64(1), 64((2) . . .are concentrically arranged. For example, the secondary coil 64 may havea series-connected single-wound or multi-wound concentric coil, or acapacitor 120 provided in the loop of the entire coil as shown in FIG.19. Alternatively, the secondary coil 64 may have a spiral shape, whichis not shown.

Further, in case that the capacitor is provided in the loop of thesecondary coil 64, the series resonance may be easily generated in theloop and, thus, a small Q value causes the series resonance rapidlychanged. This makes it difficult to control the secondary coil 64 orcauses discrepancy in each coil. Accordingly, in order to prevent suchdisadvantage, it is preferable to use a relatively high-resistivitymetal or semiconductor (e.g., silicon crystal doped with N or P to haveconductivity, or the like) as a material of the secondary coil 64.Alternatively, in addition to the capacitor, a resistor may be provided.

In the meanwhile, it is known that the resistivity of the resistorinserted into the loop of the secondary coil 64 from the outside or theresistivity of the coil body is increased as the temperature isincreased. In case that the regular RF power RF_(H) is supplied to theRF antenna 54, the amount of the RF power RF_(H) consumed is increasedas the resistivity of the secondary coil 64 is increased. Resultantly,it is expected that the amount of the current flowing to the primarycoil 62 is decreased. Accordingly, it is possible to prevent asignificantly large current from flowing to one coil. Further, it can beexpected that the current flowing in the RF antenna 54 is automaticallymade uniform.

Besides, it is preferable to cool the RF antenna 54, especially thesecondary coil 64, by using an air-cooling method or a water-coolingmethod. As such, in the case of cooling the coil 64(62), by changing thecooling temperature, it is possible to adjust the resistivity of thecoil 64(62), to thereby control the current flowing in the coil 64(62).

Meanwhile, the shape of the loops of the primary coil 62 and thesecondary coil 64 included in the RF antenna 54 is not limited to thecircular shape. The loops thereof may have a quadrangular shape, ahexagonal shape or the like. The cross sectional shapes of the primarycoil 62 and the secondary coil 64 are also not limited to the rectangle.The cross sectional shapes may have a circular shape, an ellipticalshape or the like. Further, instead of the single wire, the twisted wiremay be employed.

In the aforementioned embodiments of the present invention, theconfiguration of the inductively coupled plasma etching apparatus ismerely an example. Various modifications of the units of theplasma-generation mechanism and units having no direct involvement inthe plasma generation may be made.

For example, the RF antenna 54 may have various outer shapes such as adomical shape instead of the planar outer shape. Moreover, a processinggas may be supplied through the ceiling of the chamber 10 from theprocessing gas supply unit, and no DC bias controlling RF power RF_(L)may be supplied to the susceptor 12.

In the above embodiments, the inductively coupled plasma processingapparatus or the plasma processing method therefor is not limited to thetechnical field of the plasma etching, but is applicable to other plasmaprocesses such as a plasma CVD process, a plasma oxidizing process, aplasma nitriding process and the like. In the embodiments, the targetsubstrate to be processed is not limited to the semiconductor wafer. Forexample, the target substrate may be one of various kinds of substrates,which can be used in a flat panel display (FPD), a photomask, a CDsubstrate, a print substrate or the like.

In accordance with the present invention, it is possible to provide aninductively coupled plasma processing apparatus and a plasma processingmethod therefor, capable of improving the uniformity and controllabilityof plasma density distribution, with a simple configuration of its RFantenna that can easily be manufactured, since loads of its RF powersupply system become small by the above-mentioned configurations andoperations.

While the invention has been shown and described with respect to theembodiments, it will be understood by those skilled in the art thatvarious changes and modifications may be made without departing from thescope of the invention as defined in the following claims.

1. A plasma processing apparatus comprising: a processing chamberincluding a dielectric window; a substrate supporting unit, provided inthe processing chamber, for mounting thereon a target substrate to beprocessed; a processing gas supply unit for supplying a desiredprocessing gas to the processing chamber to perform a desired plasmaprocess on the target substrate; a first RF antenna, provided on thedielectric window, for generating a plasma from the processing gas by aninductive coupling in the processing chamber; and a first RF powersupply unit for supplying an RF power to the first RF antenna, the RFpower having an appropriate frequency for RF discharge of the processinggas, wherein the first RF antenna includes a primary coil provided on orabove the dielectric window and electrically connected to the first RFpower supply unit through an RF power supply line; and a secondary coilprovided at a portion such that the coils are coupled with each other byan electromagnetic induction therebetween, the secondary coil beingarranged closer to a bottom surface of the dielectric window than theprimary coil.
 2. The apparatus of claim 1, wherein an electric field isinduced in the processing chamber by an induced current flowing throughthe secondary coil, and a plasma is generated from the processing gas bythe induced electric field.
 3. The apparatus of claim 1, wherein thesecondary coil is electrically floated from the primary coil.
 4. Theapparatus of claim 1, wherein the primary coil and the secondary coilare arranged in parallel with the dielectric window.
 5. The apparatus ofclaim 1, wherein at least one part of the secondary coil is provided inthe dielectric window or the processing chamber.
 6. The apparatus ofclaim 1, further comprising: a second RF antenna, provided around thedielectric window independently from the first RF antenna, forgenerating a plasma from the processing gas by an inductive coupling inthe processing chamber; and a second RF power supply unit for supplyingan RF power to the second RF antenna, the RF power having an appropriatefrequency for RF discharge of the processing gas.
 7. The apparatus ofclaim 1, wherein one or more capacitors are provided in one or moreloops of the secondary coil.
 8. The apparatus of claim 7, wherein thecapacitors are variable capacitors, and capacitances of the capacitorsare adjusted to control a radial distribution of a plasma density on thetarget substrate.
 9. The apparatus of claim 1, wherein the secondarycoil is formed of a combination coil including a plurality of endlesscoils having different diameters that are concentrically arranged. 10.The apparatus of claim 9, wherein a capacitor is provided in a loop ofat least one of the endless coils.
 11. The apparatus of claim 10,wherein the capacitor is a variable capacitor, and a capacitance of thecapacitor is adjusted to control a radial distribution of a plasmadensity on the target substrate.
 12. The apparatus of claim 9, whereinthe primary coil is formed of a multi-wound concentric coil, and aplurality of wound portions of the primary coil respectively opposite tothe endless coils of the secondary coils.
 13. A plasma processing methodcomprising: arranging a target substrate to be processed at apredetermined portion below a dielectric window in a processing chamberincluding the dielectric window; supplying a desired processing gas tothe processing chamber from a processing gas supply unit; maintaining adepressurized state of the processing chamber at a predeterminedpressure level; supplying an RF power having a preset frequency from anRF power source to a primary coil arranged on or above the dielectricwindow to allow an RF current to flow through the primary coil; inducinga current through the RF current by an electromagnetic induction toallow the induced current to flow through a secondary coil arrangedcloser to a bottom surface of the dielectric window than the primarycoil; generating a plasma from the processing gas close to thedielectric window in the processing chamber by an induced electric fieldand an RF power magnetic field generated by the induced current flowingthrough the secondary coil; diffusing the generated plasma in theprocessing chamber; and performing a desired plasma process on thetarget substrate by using the plasma.
 14. The method of claim 13,further comprising: providing one or more variable capacitors in one ormore loop of the secondary coil; and controlling variously capacitancesof the variable capacitors depending on adjustment, change andconversion of process conditions in the plasma process performed on onetarget substrate.